Confused: trip odometer vs. odometer?
 

Sorry, I am totally over-thinking this probably, but if I use my trip odometer to track miles how exactly does this work? Am I entering the data for a fuel up after the tank has been used?

So, I fuel up my car on 8/18/08, write down the price I paid and the gallons I bought. Drive my car, when the tank is near E, I fuel up again on 8/25, write down the trip odometer total before I reset it and enter that into fuelly with the gallons & price from 8/18, and again, hold onto the gallons and price info for 8/25 until I get to E again. Is that about right?

I think you're confused. The first reading you enter will be used as a starting point., so it doesn't matter how much fuel you put in. You just need to know that your tank is full, so that the next time you fill up, you know exactly how much fuel you're replacing.

The forumula is:

New odometer reading - old odometer reading)/gallons of fuel. = mpg

Example Timeline:

1st fuel up: odometer = 1000, gallons = *doesn't matter*

2nd fuel up: odometer = 1200, gallons = 10

(1200-1000)/10 = 20mpg

3rd fuel up: odometer = 1500, gallons = 10

(1500-1200)/10 = 30mpg

etc.

That's it. Every time you fuel up, you write the trip odometer total and you reset the trip odometer.

I think you might be getting tripped up on the terminology.

Tripometer - you have to reset this to zero every time you fill up, and if you are tracking via this method, you just enter in the total miles right before you zero it out again as you leave the gas station

Odometer - you just track your car's total miles ever driven, but the first time you enter data, it gets ignored, since Fuelly does the math based off that first tank (so the second tank has the first measure of distance driven on that tank).

We have a page explaining this as well.

Thanks to both comments, I do understand how the odometer option works, I was curious about the trip odometer method as I have always reset it when I fuel.

So, I was thinking, today my trip odometer said 290mi when I put gas in, but I surely don't want to enter the gallons and price I paid today along with that 290, because that would be inaccurate, the 290 is what I put on the last tank of gas and has nothing to do with today's purchase.

I guess I had to write it down and physically see it so that it made sense.

I think you could take the 290 miles and divide by the total gallons used to fill up your tank and get your MPG, provided the last time you filled your tank entirely as well.

If you're trying to track which brand of gasoline performs best or something, then yes, your mileages will be offset by one from your filling stations/ price paid. Today I filled up at a Citgo for $3.99/g and calculated 29.3 mpg, but that was from the Shell station I hit last week for $3.80/g.